Electronic – PC14 and PC15 on STM32F401 not working as inputs

I'm trying to use PC14 and PC15 on Nucleo F401RE board, as inputs using this simple code:

  RCC_LSEConfig(RCC_LSE_OFF);


  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);

  // initialize ID pins as inputs
  GPIO_InitTypeDef gpio_init_struct;
  GPIO_StructInit(&gpio_init_struct);
  gpio_init_struct.GPIO_Mode = GPIO_Mode_IN;
  gpio_init_struct.GPIO_PuPd = GPIO_PuPd_UP;
  gpio_init_struct.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
  GPIO_Init(GPIOC, &gpio_init_struct);


  // read ID pins
  uint8_t inputs_state = 0;
  inputs_state |= GPIO_ReadInputDataBit(GPIOC, GPIO_Pin_13);
  inputs_state |= GPIO_ReadInputDataBit(GPIOC, GPIO_Pin_14) << 1;
  inputs_state |= GPIO_ReadInputDataBit(GPIOC, GPIO_Pin_15) << 2;

Unfortunately, while PC13 works as expected, PC14 and PC15 always stay high in case of pull-up configuration or low in case of pull-down.

The reference on page 155 states:

The LSE oscillator pins OSC32_IN and OSC32_OUT can be used as
general-purpose PC14 and PC15 I/Os, respectively, when the LSE
oscillator is off. The PC14 and PC15 I/Os are only configured as LSE
oscillator pins OSC32_IN and OSC32_OUT when the LSE oscillator is ON.
This is done by setting the LSEON bit in the RCC_BDCR register. The
LSE has priority over the GPIO function.

So I'm setting LSE off, but still no result. What am I missing?